@kted This is a standard type two diaphragm as @slt1 used, but as my tanks are sealed and underground the 100% humidity would kill them fairly quickly. There is no advantage over the button head in terms of accuracy, the button type allows the Node to be distant from the measuring point and are waterproof. Most of these US can be operated in various modes by changing the value of one of the resistors, but not all can be operated down to 3v...